Well just because you've managed to insert a script does not mean you are done with it, a lot of scripts are plug and play, meaning that you do not have to do anything.
But some scripts give you the option to edit things to suit them to your needs.
For example, the versus pop-up script by Modern Algebra allows you to edit some things
Notice how there was a header saying "Editable Region", well that means from there on, you can edit things. Once you leave the editable region, you DO NOT TOUCH anything.
The green text is just telling you what things do, you don't edit that.
What you do edit is this
The instructions for editing them were in the green text above, but to further explain some things, you ONLY edit what is after the equals sign ( = )
and if you see something like this
MAVP_SE = ["Battle2"]
You only edit what is inside of the two [ ].
It is recommended that once you install a script, you start a new game on your project rather replaying from a previous save game, it is a known occurrence that some scripts require you to start a new game before it will work.